Method of air conditioning



Oct. 8, 1935.

H O. FORREST METHOD OF AIR CONDITIONING Fi'led Aug.

.NBNQKNNBAN A '.IIIIII INVENTOR ATTORNE Patented Oct. 8, 1935 UNITEDv STATES PATENT OFFICE 2,011,027 METHOD or Am CONDITIONING Henry 0. Forrest, Teaneck, N. J.

pplication August 19, 1931, Serial No. 557,959

2 Claims. (Cl. 261--11) This invention relates to air conditioning, and relates more particularly to a process for the conditioning of air for rooms, residences and other buildings, with respect to its dry bulb tempera- 5 ture and relative humidity for the purpose of alleviating physical discomfort caused by excessive dry bulb temperature or excessive humidity, or both.

According to this invention, I rst dehumidify the air to a relative humidity lower than that necessary for comfort, preferably by the use of a liquid dehumidifying or dehydrating agent, and then cool the air by rehumidifying it to a higher relative humidity (but within the comfort range) by the use of an open spray of water. The dehumidifying step is preferably carried out without increase in the temperature of the air being conditioned, and may advantageously be conducted substantially isothermally so far as the air temperature is concerned. In order to accomplish this and at the same time permit protracted use of the dehydrating agent, it is necessary to remove the heat of absorption from the dehydrating agent by suitable cooling means during its use in the dehumidifying step.

'I'he step of cooling the air by humidifying it with a water spray is preferably accomplished substantially adiabatically, since available cooling water is ordinarily at a temperature above that of the wet bulb temperature of the air being humided and only by adiabatic evaporation can the cooling water be reduced to the desired wet bulb temperature and used repeatedly. Of course, if the available cooling water were below the wet bulb temperature, and its repeated use were not deemed desirable, the cooling and humidiiication step could be eected without resorting to adiabatic evaporation.

By the combined steps of dehumidication and humidification as described above, I avoid the necessity of refrigerating the air or the cooling water by special refrigeration apparatus. So far as I am aware, all prior systems of air condiregeneration. For practical reasons, it is desir- Y able that it be such as to be capable of being regenerated simply by driving off the absorbed water by heating., Although solid dehydrating agents or absorbents of this character are known and may be employed in my process, I prefer to use liquid dehydrating agents as they lend themselves readily to the development of inexpensive and compact apparatus capable of being operated either continuously or intermittently as desired. 5

One of the primary objects of this invention is to accomplish the conditioning of air with respect to its temperature and humidity without the use of refrigeration in the accepted sense of the term. 10

Another object of this invention is to dehumidify air by the use of liquid dehydrating agents.

Other objects and advantages of this invention will be apparent from the following description, taken in commotion with the accompany- 15 ing drawing, in which: v,

The figure is a schematic layout of an apparatus adapted for continuously conditioning air in accordance with my novel method.

Referring more particularly to the drawing, 20 the space to be conditioned is diagrammatically represented at I0, and is provided with an outlet register Il and an inlet register l2 connected respectively to an outlet air duct I3 and' inlet air duct I4. It will be understood that where the g5 space to be conditioned is an entire building, there will be` a plurality of inlet and outlet registers which may connect into a common outlet duct I3 and a common inlet duct Il, respectively. The outlet'register will ordinarily be located near 30 the top of the space to be conditioned and the inlet register near the bottom, as shown in the drawing, although this arrangement is not essential and may be varied if desired.

Air to be conditioned is withdrawn from the 35 space I0 through the outlet duct I3 by the air pump I5, and discharged into a dehumidifier I 6. 'I'he dehumidifier I6 is shown as divided into four sections I1 by spaced baiiles I8. The air tobe dehumidifled flows through the dehumidifier' I6 40 from an inlet I9, into which a pump I5 discharges,

to an outlet 20, passing through each of the baffles I8 in turn. The bottoms of the baiiies I8 are imperforate and constitute dams of increasing height from the air inlet end to the airoutlet 45 end of the dehumidifier. The liquid dehydrating agent, which may be, for example, a concentrated solution of calcium chloride brine, may be introduced into the last or air outlet section I1 of the dehumidier I6 near the bottom thereof through .0 the pipe 2|, and forms a pool 22 of liquid dehydrating agent in said last section I'I. The dehydrating agent overiiows from the pool 22 into a pool 23 in the next section I1, thence into a pool 24 in the succeeding section and finally into the bottom 25-of the i'irst or air inlet section I1. It

.f will be understood that the height of each pool is ldetermined by the height of the imperforate lower portionof the baiiles I3.

Separate pumps 5, which may if desired be driven by a common prime mover 28, pick up the liquid dehydrating agent'from the bottom of each section I1 and introduce the same into the top of the same section through spray nozzles 21. Obviously a plurality of spray nozzles may be used in each section.

The liquiddehydratlng agent-in passing downwardly in the form of a line spray through the air passing through the dehumidifier, absorbs moisture from the same and consequently reduces thevabsolute humidity'of -the air being conditioned. By virtue of the location of the air inlet and the arrangement of chambers I1 and pools 22, 23,24 and 25, the dehydrating agent when at a point of highest concentration contacts'air in a zone of least moisture content so that increased eiiciency of dehydration is efi'ected by what is substantially a counterow arrangement of air and dehydrating agent.

A part of the dehydrating agent circulated by the pump 5 connected to the first section I1 is diverted through a pipe 28 to a heat exchanger 29 and thence to an evaporator 30. The part of the dehydrating agent diverted and regenerated may be concentrated to a higher degree than necessary for effecting absorption and this regen= hydrating iiuid to the desired degree of concentration. l

'I'he evaporator 30 is heated by a heating element indicated diagrammatically at 3|, and may be of any suitable construction adapted to heat the dehydrating agent to expel the absorbed water therefrom such as a gas burner, an eleci tric heater or a steam coil. The water thus removed from the dehydrating agent is discharged to the outside air through a pipe 32 in the form of steam or water vapor. The regenerated dehydrating agent which is at high temperature is picked up by a pump 33, forced through the heat exchanger 29 countercurrent to the dehydrating agent about to be regenerated transferring most of its sensible heat thereto, and thence is delivered to a suitable cooler 34. In the cooler 34 the regenerated dehydrating agent is cooled by indirect heat exchange with either cooling water or outside air or other cooling agent, as desired, to a temperature approidmating that of the air to be conditioned, and is then discharged through a pipe 2| to the dehumidifier I6 as described above. f

The dehumidied air is discharged from the dehumidifier I6 through the outlet 20 and introduced into a humidifier chamber 40. Water is sprayed into the top of the humidifier 40 through the spray nozzle 4I, and is recirculated from the bottom of' the chamber 40 back to the nozzle 4| by means of a pump 42. Additional Water to compensate for that removed by evaporation in the chamber 40 may be supplied from time to time as required from any suitable source, such as a supply pipe 43. Since the Water used in the chamber 40 is recirculated continuously and only a small percentage of the total water in circulation is evaporated, the water rapidly assumes the wet bulb temperature of the air. The system is preferably insulated so that there is little heat interchange with the surrounding atmosphere.

Under these conditions, adiabatic evaporation of the Water into the air takes place, the sensible heat necessary for this evaporation being taken from the air and reducing its dry bulb temperature while increaslng'its relative humidity. viously, the fractional humidiiications thus obtained must be so controlled that the final relative humidity of the air is within the comfort range for air of the temperature in question. The

air so conditioned is then returned to the space 10 I0 through the inlet duct I4.

In order to remove the heat produced by the absorption of the water in the dehydrating agent in the dehumidifier I8, water is continuously circulated through closed cooling coils 50 immersed 15 in the pools-22, 23 and 24 in the bottom of the dehumidifier by a pump 5| and suitable inlet Pipes 52. After passing through the coils 50, the cooling water is conducted through a pipe 53 to the top of a water cooling tower 55 of con- 20 ventional construction, from the bottom of which the pump 5| takes its suction. In the water cooling tower 55, the cooling water is reduced in temperature by evaporation in contact with the outside air in the well known manner. If 25 v desired, the cooler 34 may be connected in circuit with the pump 5| and tower 55 as shown. An air outlet 51 with a blower 58 may be associated with the tower 55 to improve air circulation in the tower and aid in thel removal of heat.

Where city water or other plentiful source of cooling`water of sufficiently low temperature is available, the coolingtower 55 may be omitted, and. the cooling water run to waste after passing through the cooling coils 50.

In order to supply fresh air for ventilation, outside air may be admitted to the inlet ofthe pump I5 through-a conduit 54 as required.

As an example of the carrying out of my invention, the following figures are given, simply 40 by way of illustration. Let us assume that the. air discharged from the pump I5 is at a temperature of F. and has a relative humidity of 47%. This air, of course, comprises an admixture of the air withdrawn from the space I0 to 45 Vbe conditioned and the fresh air (say 20%) for Ventilating purposes admitted from the outside. Let us assume further that the dehydrating agent is a 48% solution of calcium chloride brine and is introduced, into the dehumidifier I6 at this 50 same temperatureof 85 F. and is maintained at that temperature by the cooling water circulated through the cooling coils 50. It will be apparent that undery these conditions the air leaving the dehumidifier will still be at a temper- 55 ature of 85 F. but that its relative humidity will be reduced. The amount of reduction of the relative humidity will, of course, depend upon the rate of circulation of the dehydrating agent and its water absorbing properties, but it is perfectly 60 practicable under the conditions stated, to reduce the relative humidity to 30%. The air entering the humidifier 40 will therefore be at a temperature of 85 F. and have a relative humidity of 30%. By proper design of the humidifier 35 40, it is readily possible to secure a cooling of the air of 10 F. by adiabatic evaporation. Under such conditions, we may determine from the standard humidity chart that thev air leaving the humidifier 40 will have a relative humidity 70 of 54%. Air at a temperature of 75 F. and a relative humidity of 54% will result in a somewhat higher temperature and lower relative humidity in the conditional area I0, which would be found very comfortable, both to people stay- 75 ing in the space I0 for long periods and to those only passing through or present forv short periods of time, in comparison with outside atmospheric conditions of say 85 F. and 75% re1- ative humidity which would'produce the entering mixture at the pump l5 referred to.

Instead of using calcium chloride brine as a dehydrating agent, other hygroscopic substances having a strong ainity for water may be employed, for example; a caustic soda solution, glycerine or triethanol amine. A

It is further contemplated as a part of this invention that some purifying agent such as a. weak solution of calcium hydroxide may be substituted for water in the humidifier 40. In case such an agent were used, in addition tothe humidifying action taking place as described inconnection with the humidier, an appreciable amount of carbon dioxide would be removed from the air resulting in its purification. The precipitated calcium carbonate resulting from such an action could be removed in any manner desired as by setting, and more calcium hydroxide could be added to the system as needed.

The dehumidiiying apparatus used for carrying my novel method into practice has been described as delivering the dehydrated air to the humidifier at the same temperatures at which it was received. Obviously, however, by controlling the quantity or the temperature of the cooling water circulating through the coils or by controlling the temperature of the water or purifying medium utilized in the humidifier, temperaature control. of the air may be eiective in either place desired either by simultaneous-regulation or independently oi' each other.

A zone of greater concentration.

Although my novel method is especially advantageos when it is desired to impart desired characteristics of temperature and humidity to air by utilizing a step that involves cooling the air, it *is*l obvious that by circulating a heating 5 medium4 through the coils 50' by spraying the dehydrated air with a hot iluid or vapor in the humidifier;- or by spraying the'air by a heated uid of proper hydration characteristics in the dehumidier that cold air may be heated to a 10 desired temperature within the healthfulcomfort range while being given desired characteristics of humidity so that the novel method may be used when it is desired to condition air in winter aswell as in the summer time. 15

I claim:

1. A method of conditioning air which includes the steps of contacting said air with a circulated hygroscopic liquid of controlled concentration and dehydrating said air to a high degree while zo' continuously removing heat of absorption from said hygroscopic liquid, and contacting said air with a spray of water and imparting thereto conditions of temperature and humidity to place it within the comfort range.

2. A method of conditioning air which includes the steps of progressively subjecting said air to the action of a circulated hygroscopic liquid in zones of varying concentration of said liquid, removing heat of absorption from said liquid between points of contact in said zones, withdrawing a portion of said liquid from a zone of lesser concentration, regenerating said withdrawn pox'-v tion, and returning said regenerated liquid to a $5 HENRY O. FORRFST. 

